The Collegiate Church of Saint Gertrude is a historical building in Nivelles, Wallonia, Belgium consecrated in 1046 by Wazo, bishop of Liège, in the presence of emperor Henry III. It is an example both of Mosan art and of Ottonian architecture.
Claudine Ronnay-Docmans writes in the Patrimoine majeur de Wallonie that the interior dimensions recall: "the splendour of the Ottonian liturgy, as people is able to know it for the abbey of Essen (Germany)".
The Westwork has been reconstructed. Its current appearance is the result of a long reconstruction finished in 1984, following severe damage through bombing in May 1940.